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The kinetics of labeled derivatives of apamin were studied in vitro and in vivo in mice by Cheng-Raude et al. This shed some light on the kinetics of apamin itself. The key organ for excretion is likely to be the kidney, since enrichment of the labeled derivatives was found there. The peptide apamin is small enough to pass the glomerular barrier, facilitating renal excretion. The central nervous system, contrarily, was found to contain only very small amounts of apamin. This is unexpected, as this is the target organ for neurotoxicity caused by apamin. This low concentration thus appeared to be sufficient to cause the toxic effects.
However, these results disagree with a study of Vincent et al. After injection of a supralethal dose of radioactive acetylated apamin in mice, enrichment was found in the spinal cord, which is part of the target organ. Some other organs, including kidney and brain, contained only small amounts of the apamin derivative. | 1 | Biochemistry |
The shutter is fitted to the dimensions of the masonry opening. The pintle is embedded or surface mounted to the structure itself. The pintle pin is positioned on the outside corner of the masonry. This approach can be seen on brick structures, especially post-civil war commercial multi-story buildings. Also common in the south of Europe, France, Italy, and Austria, it allows the shutter to sit almost fully parallel to the structure.
The European structures are typically stucco coated, with a drive type pintle built diagonally into the masonry prior to stucco finish. A lag screw pintle can be substituted for the drive pintle. Brick structures can employ a similar embedded pintle, or a surface mounted pintle. Storm type strap hinges are typically in Europe. American examples are often tapered. | 8 | Metallurgy |
A DNA adduct is a segment of DNA that binds to a chemical carcinogen. Some adducts that cause lesions to DNA included oxidatively modified bases, propano-, etheno-, and MDA-induced adducts. 5‐Hydroxymethyluracil is an example of an oxidatively modified base where oxidation of the methyl group of thymine occurs. This adduct interferes with the binding of transcription factors to DNA which can trigger apoptosis or result in deletion mutations. Propano adducts are derived by species generated by lipid peroxidation. For example, HNE is a major toxic product of the process. It regulates the expression of genes that are involved in cell cycle regulation and apoptosis. Some of the aldehydes from lipid peroxidation can be converted to epoxy aldehydes by oxidation reactions. These epoxy aldehydes can damage DNA by producing etheno adducts. An increase in this type of DNA lesion exhibits conditions resulting in oxidative stress which is known to be associated with an increased risk of cancer. Malondialdehyde (MDA) is another highly toxic product from lipid peroxidation and also in the synthesis of prostaglandin. MDA reacts with DNA to form the M1dG adduct which causes DNA lesions. | 1 | Biochemistry |
Metal bipyridine as well as related phenanthroline complexes are generally bioactive, as they can act as intercalating agents. | 5 | Photochemistry |
In organosulfur chemistry, a sulfenyl chloride is a functional group with the connectivity , where R is alkyl or aryl. Sulfenyl chlorides are reactive compounds that behave as sources of . They are used in the formation of and bonds. According to IUPAC nomenclature they are named as alkyl thiohypochlorites, i.e. esters of thiohypochlorous acid.
Typically, sulfenyl halides are stabilized by electronegative substituents. This trend is illustrated by the stability of obtained by chlorination of carbon disulfide. | 0 | Organic Chemistry |
Junes Ipaktschi grew up in Tehran / Iran. After graduation in June 1958 at the Razi School in Tehran, he studied chemistry from 1958 to 1966 at the Heidelberg University. His doctoral thesis dealt with the field of Organic Chemistry under the direction of Heinz Staab. He then conducted research as an assistant in the same working group and habilitated in 1972 for the Organic Chemistry with a thesis on the photochemistry of unsaturated ketones. From 1972 to 1974 he did research as a postdoctoral fellow and visiting professor in the laboratory of William G. Dauben at the University of California, Berkeley. In 1973 he accepted an appointment at the Department of Chemistry at the University of Marburg and became a professor.
In 1975 he was at the chemical Institute of Arya Mehr University (now Sharif University) appointed to Tehran and joined as a professor in his native country, Iran. In 1978 he moved to the newly founded Reza Shah Kabir University (now Mazandaran University) and worked there as a professor for chemistry. He was for a time as director of the University and also head of the Chemical Institute operates. From 1980 until retirement, in 2005, he was professor of chemistry at the University of Giessen. 1992–1995 he was dean of the chemistry department of the University and 2001–2002 executive director of the Organic Chemical Institute there. In addition to several visits as a visiting professor at various universities in Iran, he was invited in 2001 as a visiting professor at the National Institute of Advanced Industrial Science and Technology, Tsukuba / Japan and spent three months there. In 1999, Ipaktschi was awarded the Kharazmi Award. | 0 | Organic Chemistry |
Heterogeneous photocatalysis is the process that underpins the activity of most architectural materials, such as glass, ceramic tiles, roof tiles, concrete, paint, and fabrics which are promoted as being self-cleaning (or air-purifying). These photocatalytic materials facilitate the oxidative mineralisation of organic and inorganic species by ambient oxygen on their surfaces, rendering the surfaces clean and, usually, hydrophilic. In most commercial photocatalytic products the active layer is a thin, clear, colourless coating of the semiconductor anatase titania, which requires UV light to photogenerate the necessary electrons (e) and holes (h), in its conductance and valence bands, respectively, to promote the photocatalytic process. A schematic of the key processes behind the photocatalytic mineralisation of an organic pollutant on the surface of a titania photocatalyst film is illustrated in figure 1 and the overall reaction is summarised by:
Water molecules—adsorbed to the photocatalyst—are also needed to generate the hydroxyl groups on the surface.
The marketing of photocatalytic products and prevention of counterfeiting is made difficult because the photocatalytic coatings are usually and necessarily invisible to the eye. One way to achieve a visual demonstration of photocatalysis is to use a dyestuff, like methylene blue, dissolved in water, as the organic species to be mineralised, since, as the photocatalytic process proceeds, the colour of the dye disappears as it is oxidised. This approach forms the basis of a well-established ISO test for photocatalytic activity of films ISO. However, most photocatalyst commercial products use only a thin layer of titania (e.g. ca. 15 nm thick in self-cleaning glass) and ambient UV levels are often low (e.g. for a sunny day in the UK the UVA irradiance is only ca. 4 mW/cm). As a consequence, the photocatalytic oxidative bleaching of methylene blue is usually very slow, taking many hours, and so inappropriate for marketing at least. | 5 | Photochemistry |
Most knowledge about cys-loop receptors comes from inferences made while studying various members of the family. Research on the structures of [http://www.proteopedia.org/wiki/index.php/Acetylcholine_binding_protein acetylcholine binding proteins] (AChBP) determined that the binding sites consist of six loops, with the first three forming the principal face and the next three forming the complementary face. The last loop on the principal face wraps over the ligand in the active receptor. This site is also abundant in aromatic residues.
Recent literature indicates that the Trp residue on loop B is crucial for both agonist and antagonist binding. The neurotransmitter is taken into the binding site where it interacts (through hydrogen and cation-π bonding) with the amino acid resides in the aromatic box, located on the principal face of the binding site. Another essential interaction occurs between the agonist and a tyrosine on loop C. Upon interaction, the loop undergoes a conformational change and rotates down to cap the molecule in the binding site. | 1 | Biochemistry |
Commercially available nitric acid is an azeotrope with water at a concentration of 68% . This solution has a boiling temperature of 120.5 °C (249 °F) at 1 atm. It is known as "concentrated nitric acid". The azeotrope of nitric acid and water is a colourless liquid at room temperature.
Two solid hydrates are known: the monohydrate or oxonium nitrate and the trihydrate .
An older density scale is occasionally seen, with concentrated nitric acid specified as 42 Baumé. | 3 | Analytical Chemistry |
Fine chemicals account for about 4% of the universe of chemicals. The latter, valued at $2,500 billion, is dominated mainly by oil-, gas-, and mineral-derived commodities (~40%) on one hand and a large variety of specialty chemicals at the interface between industry and the public on the other hand (~55%). The global production value of fine chemicals is estimated at $85 billion, of which about 2/3, or $55 billion are produced captively and $30 billion represent the global revenues of the fine chemical industry. The corresponding figures for the major user, the pharmaceutical industry, are $32 billion and $23 billion, respectively. For a number of reasons, such as the lack of statistical data and the somewhat equivocal definition it is not possible to exactly determine the size of the fine chemical market.
In Table 5, the approximately $85 billion fine chemical market is subdivided into major applications according to their relevance, namely, fine chemicals for pharmaceuticals, agrochemicals and specialty chemicals outside life sciences. Furthermore, a distinction is made between captive (in-house) production and merchant market. Pharmaceutical fine chemicals (PFCs) account for two-thirds of the total. Out of the PFC value of $55 billion, about $23 billion (~40%) are traded, and $32 billion (~60%) are the production value of the pharma industry's in-house production. Within life science products, fine chemicals for agro, and —at a distance— for veterinary drugs follow in importance. The production value for fine chemicals used for specialty chemicals other than pharmaceuticals and agrochemicals is estimated at $15 billion. As the leading specialty chemical companies, Akzo Nobel, Dow, DuPont, Evonik, Chemtura and Mitsubishi are backward-integrated, the share of in-house production is estimated at 75%, leaving a merchant market of approximately $5 billion. | 0 | Organic Chemistry |
The internal cavity of a carcerand can be as large as 1700 Å (1.7 nm) when six hemicarcerands form a single octahedral compound. This is accomplished by dynamic covalent chemistry in a one-pot condensation of 6 equivalents of a and 12 equivalents of ethylene diamine with trifluoroacetic acid catalyst in chloroform at room temperature followed by reduction of the imine bonds with sodium borohydride. | 6 | Supramolecular Chemistry |
Marrow is part of I'm a Scientist, Get me out of here! energy generation zone. He has also been a key developer and academic consultant for the Dissemination of IT for the Promotion of Materials Science (DoITPoMS). Global Cycle Network Technology (GCN Tech) interviewed James about carbon fibre fatigue and strain in 2022. | 8 | Metallurgy |
tert-butyllithium is a pyrophoric substance, meaning that it spontaneously ignites on exposure to air. Air-free techniques are important so as to prevent this compound from reacting violently with oxygen and moisture:
:t-BuLi + O → t-BuOOLi
:t-BuLi + HO → t-BuH + LiOH
The solvents used in common commercial preparations are themselves flammable. While it is possible to work with this compound using cannula transfer, traces of tert-butyllithium at the tip of the needle or cannula may ignite and clog the cannula with lithium salts. While some researchers take this "pilot light" effect as a sign that the product is "fresh" and has not degraded due to time or improper storage/handling, others prefer to enclose the needle tip or cannula in a short glass tube, which is flushed with an inert gas and sealed at each end with septa. Serious laboratory accidents involving tert-butyllithium have occurred. For example, in 2008 a staff research assistant, Sheharbano Sangji, in the lab of Patrick Harran at the University of California, Los Angeles, died after being severely burned by a fire ignited by tert-butyllithium.
Large-scale reactions may lead to runaway reactions, fires, and explosions when tert-butyllithium is mixed with ethers such as diethyl ether, and tetrahydrofuran. The use of hydrocarbon solvents may be preferred. | 0 | Organic Chemistry |
Many nickel-based superalloys depend on solid solution as a strengthening mechanism. The most popular example is the Inconel family, where many of these alloys contain chromium and iron and some other additions of cobalt, molybdenum, niobium, and titanium. The nickel-based superalloys are well known for their intensive use in the industrial field especially the aeronautical and the aerospace industry due to their superior mechanical and corrosion properties at high temperatures. | 8 | Metallurgy |
The presence of an interface influences generally all thermodynamic parameters of a system. There are two models that are commonly used to demonstrate interfacial phenomena: the Gibbs ideal interface model and the Guggenheim model. In order to demonstrate the thermodynamics of an interfacial system using the Gibbs model, the system can be divided into three parts: two immiscible liquids with volumes and and an infinitesimally thin boundary layer known as the Gibbs dividing plane () separating these two volumes.
The total volume of the system is:
All extensive quantities of the system can be written as a sum of three components: bulk phase , bulk phase , and the interface . Some examples include internal energy , the number of molecules of the th substance , and the entropy .
While these quantities can vary between each component, the sum within the system remains constant. At the interface, these values may deviate from those present within the bulk phases. The concentration of molecules present at the interface can be defined as:
where and represent the concentration of substance in bulk phase and , respectively.
It is beneficial to define a new term interfacial excess which allows us to describe the number of molecules per unit area: | 7 | Physical Chemistry |
The American Society of Mechanical Engineers (ASME) has developed two separate and distinct standards on temperature Measurement, B40.200 and PTC 19.3.
B40.200 provides guidelines for bimetallic-actuated, filled-system, and liquid-in-glass thermometers. It also provides guidelines for thermowells.
PTC 19.3 provides guidelines for temperature measurement related to Performance Test Codes with particular emphasis on basic sources of measurement errors and techniques for coping with them. | 7 | Physical Chemistry |
Reactions are known where the deuterated species reacts faster than the undeuterated analogue, and these cases are said to exhibit inverse kinetic isotope effects (IKIE). IKIE's are often observed in the reductive elimination of alkyl metal hydrides, e.g. (MeNCHCHNMe)PtMe(H). In such cases the C-D bond in the transition state, an agostic species, is highly stabilized relative to the C–H bond.
An inverse effect can also occur in a multistep reaction if the overall rate constant depends on a pre-equilibria prior to the rate-determining step which has an inverse equilibrium isotope effect. For example, the rates of acid-catalyzed reactions are usually 2-3 times greater for reactions in DO catalyzed by DO than for the analogous reactions in HO catalyzed by HO This can be explained for a mechanism of specific hydrogen-ion catalysis of a reactant R by HO (or DO).
:HO + R RH + HO
:RH + HO → HO + P
The rate of formation of products is then d[P]/dt = k[RH] = kK[HO][R] = k[HO][R]. In the first step, HO is usually a stronger acid than RH. Deuteration shifts the equilibrium toward the more strongly bound acid species RD in which the effect of deuteration on zero-point vibrational energy is greater, so that the deuterated equilibrium constant K is greater than K. This equilibrium isotope effect in the first step usually outweighs the kinetic isotope effect in the second step, so that there is an apparent inverse isotope effect and the observed overall rate constant k = kK decreases. | 7 | Physical Chemistry |
In physics, a bipolaron is a type of quasiparticle consisting of two polarons. In organic chemistry, it is a molecule or a part of a macromolecular chain containing two positive charges in a conjugated system. | 7 | Physical Chemistry |
The Ryznar stability index (RSI) uses a database of scale thickness measurements in municipal water systems to predict the effect of water chemistry. It was developed from empirical observations of corrosion rates and film formation in steel mains.
This index is defined as:
:RSI = 2 pH – pH (measured)
* For 6.5 < RSI < 7 water is considered to be approximately at saturation equilibrium with calcium carbonate
* For RSI > 8 water is undersaturated and, therefore, would tend to dissolve any existing solid CaCO
* For RSI < 6.5 water tends to be scale form | 3 | Analytical Chemistry |
A rotation symmetry in dimension 2 or 3 must move a lattice point to a succession of other lattice points in the same plane, generating a regular polygon of coplanar lattice points. We now confine our attention to the plane in which the symmetry acts , illustrated with lattice vectors in the figure.
Now consider an 8-fold rotation, and the displacement vectors between adjacent points of the polygon. If a displacement exists between any two lattice points, then that same displacement is repeated everywhere in the lattice. So collect all the edge displacements to begin at a single lattice point. The edge vectors become radial vectors, and their 8-fold symmetry implies a regular octagon of lattice points around the collection point. But this is impossible, because the new octagon is about 80% as large as the original. The significance of the shrinking is that it is unlimited. The same construction can be repeated with the new octagon, and again and again until the distance between lattice points is as small as we like; thus no discrete lattice can have 8-fold symmetry. The same argument applies to any k-fold rotation, for k greater than 6.
A shrinking argument also eliminates 5-fold symmetry. Consider a regular pentagon of lattice points. If it exists, then we can take every other edge displacement and (head-to-tail) assemble a 5-point star, with the last edge returning to the starting point. The vertices of such a star are again vertices of a regular pentagon with 5-fold symmetry, but about 60% smaller than the original.
Thus the theorem is proved.
The existence of quasicrystals and Penrose tilings shows that the assumption of a linear translation is necessary. Penrose tilings may have 5-fold rotational symmetry and a discrete lattice, and any local neighborhood of the tiling is repeated infinitely many times, but there is no linear translation for the tiling as a whole. And without the discrete lattice assumption, the above construction not only fails to reach a contradiction, but produces a (non-discrete) counterexample. Thus 5-fold rotational symmetry cannot be eliminated by an argument missing either of those assumptions. A Penrose tiling of the whole (infinite) plane can only have exact 5-fold rotational symmetry (of the whole tiling) about a single point, however, whereas the 4-fold and 6-fold lattices have infinitely many centres of rotational symmetry. | 3 | Analytical Chemistry |
* Lewis, Peter Rhys, Reynolds, K and Gagg, C, Forensic Materials Engineering: Case studies, CRC Press (2004)
* Ezrin, Meyer, Plastics Failure Guide: Cause and Prevention, Hanser-SPE (1996).
* Wright, David C., Environmental Stress Cracking of Plastics RAPRA (2001).
* Lewis, Peter Rhys, and Gagg, C, Forensic Polymer Engineering: Why polymer products fail in service, Woodhead/CRC Press (2010). | 7 | Physical Chemistry |
During her career, Wilma Olson had won many awards, among others:
*Douglass College Medal, 2001
*American Chemical Society – North Jersey Section
*Sister Marian José Smith Excellence in Education Award, 2000
*New Jersey Woman of Achievement Award, 1998
*Wellcome Visiting Professorship, New York University, 1997
*American Women in Science, New York Area Scientist of the Year Award, 1994
*National Lecturer and National Award for Excellence and Leadership in Biophysics, Biophysical Society 1994
*National Institute of General Medical Sciences MERIT Award, 1988–98
*Rutgers University Board of Trustees Research Award, 1993
*Guggenheim Fellowship, 1978 | 1 | Biochemistry |
A lactim is a cyclic imidic acid compound characterized by an endocyclic carbon-nitrogen double bond. They are formed when lactams undergo tautomerization. | 0 | Organic Chemistry |
While only one oxhide ingot fragment has been recovered from Egypt (in the context of a LBA smelting workshop), there is a wide array of painted scenes in Egypt that show oxhide ingots. The earliest scene dates to the 15th century BC and the latest scene to the 12th century BC. The ingots display their typical four protrusions, and red paint (which suggests they are copper) is preserved on them. The captions accompanying the scenes explain that the men who bring the ingots come from the north, specifically Retnu (Syria) and Keftiu (unidentified). They are shown being carried on the shoulders of men, sitting with other goods in storage, or as part of scenes in smelting workshops. In a relief from Karnak, the pharaoh Amenhotep II is seen riding a chariot and spearing an oxhide ingot with five arrows. A laudatory caption emphasizing the pharaoh’s strength accompanies the scene.
Several of the “Amarna letters” dating to the mid-14th century BC refer to hundreds of copper talents—in addition to goods such as elephant tusks and glass ingots—sent from the kingdom of Alashiya to Egypt. Some scholars identify Cyprus with Alashiya. In particular, the Uluburun cargo is similar to the goods that, according to the letters, Alashiya sent to Egypt. | 8 | Metallurgy |
This is the standard drum filter discharge. A scraper blade, which serves to redirect the filter cake into the discharge chute, removes the cake from the filter cloth just before re-entering the vat. Scraper discharge is used if the desired separation requires high filtration rate or if heavy solid slurry is used or if the slurry is easy to filter to produce cake formation or if a longer wear resistance is desired for the separation of the mentioned slurry. | 3 | Analytical Chemistry |
The electronic structure of the thiolate-protected gold clusters is characterized by strongly pronounced quantum effects. These result in discrete electronic states, and a nonzero HOMO/LUMO gap. This existence of discrete electronic states was first indicated by the discrepancy between their optical absorption and the predictions of classical Mie scattering. The discrete optical transitions and occurrence of photoluminescence in these species are areas where they behave like molecular, rather than metallic, substances. This molecular optical behavior sharply distinguishes thiolate-protected clusters from gold nanoparticles, whose optical characteristics are driven by Plasmon resonance. Some of thiolate-protected clusters properties can be described using a model in which the clusters are treated like "superatoms". According to this model they exhibit atomic-like electronic states, that are labeled S,P,D,F according to their respective angular momentum on the atomic level. Those clusters that have a "closed superatomic shell'" configuration have indeed been identified as the most stable ones. This electronic shell closure and the resulting gain in stability is responsible for the discrete distribution of a few stable cluster sizes (magic numbers) observed in their synthesis, rather than a quasi-continuous distribution of sizes. | 7 | Physical Chemistry |
Even if we work in three dimensions here, the definitions of exact differentials for other dimensions are structurally similar to the three dimensional definition. In three dimensions, a form of the type
is called a differential form. This form is called exact on an open domain in space if there exists some differentiable scalar function defined on such that
throughout , where are orthogonal coordinates (e.g., Cartesian, cylindrical, or spherical coordinates). In other words, in some open domain of a space, a differential form is an exact differential if it is equal to the general differential of a differentiable function in an orthogonal coordinate system.
::Note: In this mathematical expression, the subscripts outside the parenthesis indicate which variables are being held constant during differentiation. Due to the definition of the partial derivative, these subscripts are not required, but they are explicitly shown here as reminders. | 7 | Physical Chemistry |
Ketazines are also important intermediates in the industrial production of hydrazine hydrate by the peroxide process. In the presence of an oxidant, ammonia and ketones react to give hydrazine via ketazine:
:2 Me(Et)C=O + 2 NH + HO → Me(Et)C=NN=C(Et)Me + 2 HO
The ketazine can be hydrolyzed to the hydrazine and regenerate the ketone:
:Me(Et)C=NN=C(Et)Me + 2 HO → 2 Me(Et)C=O + NH
Ketazines have been also used as sources of hydrazine produced in situ, for example in the production of herbicide precursor 1,2,4-triazole. | 0 | Organic Chemistry |
A grant of £670,000 was awarded in 1985 by the then Science and Engineering Research Council (SERC) to establish a national Mass Spectrometry Center at Swansea University to provide an analytical service to British Universities. It was officially opened in April 1987 by Lord Callaghan. In 2002, the center was enlarged and the new laboratories were opened by Lord Morgan. Following successful £3,000,000 contract renewal Edwina Hart, the Minister for Economy, Science and Transport, officially re-opened the EPSRC National Research Facility after refurbishment in 2015. | 3 | Analytical Chemistry |
Rhazinilam is an alkaloid first isolated in 1965 by Linde from the Melodinus australis plant. It was later isolated from the shrub Rhazya stricta as well as from other organisms. | 0 | Organic Chemistry |
Insulin affects ACC in a similar way to PDH. It leads to its dephosphorylation via activation of PP2A phosphatase whose activity results in the activation of the enzyme. Glucagon has an antagonistic effect and increases phosphorylation, deactivation, thereby inhibiting ACC and slowing fat synthesis.
Affecting ACC affects the rate of acetyl-CoA conversion to malonyl-CoA. Increased malonyl-CoA level pushes the equilibrium over to increase production of fatty acids through biosynthesis. Long chain fatty acids are negative allosteric regulators of ACC and so when the cell has sufficient long chain fatty acids, they will eventually inhibit ACC activity and stop fatty acid synthesis.
AMP and ATP concentrations of the cell act as a measure of the ATP needs of a cell. When ATP is depleted, there is a rise in 5'AMP. This rise activates AMP-activated protein kinase, which phosphorylates ACC and thereby inhibits fat synthesis. This is a useful way to ensure that glucose is not diverted down a storage pathway in times when energy levels are low.
ACC is also activated by citrate. When there is abundant acetyl-CoA in the cell cytoplasm for fat synthesis, it proceeds at an appropriate rate. | 1 | Biochemistry |
The retromer complex is highly conserved: homologs have been found in C. elegans, mouse and human. The retromer complex consists of 5 proteins in yeast: Vps35p, Vps26p, Vps29p, Vps17p, Vps5p. The mammalian retromer consists of Vps26, Vps29, Vps35, SNX1 and SNX2, and possibly SNX5 and SNX6. It is proposed to act in two subcomplexes: (1) A cargo recognition heterotrimeric complex that consist of Vps35, Vps29 and Vps26, and (2) SNX-BAR dimers, which consist of SNX1 or SNX2 and SNX5 or SNX6 that facilitate endosomal membrane remodulation and curvature, resulting in the formation of tubules/vesicles that transport cargo molecules to the trans-golgi network (TGN). Humans have two orthologs of VPS26: VPS26A, which is ubiquitous, and VPS26B, which is found in the central nervous system, where it forms a unique retromer that is dedicated to direct recycling of neuronal cell surface proteins such as APP back to the plasma membrane with the assistance of the cargo receptor SORL1. | 1 | Biochemistry |
Recent research has showed that expression of clock genes show tissue-specificity. Learning about how, when, and why specific tissues show certain peaks in clock genes like PRR can reveal more about the subtle nuances of each gene within the repressilator.
Few investigations into the circadian oscillator mechanisms in species other than A. thaliana have taken place; learning which genes are responsible for clock functions in other species will give more insight into the similarities and differences in clocks across plant species.
The mechanistic details of each step in the plant biological clock repressilator system have yet to be fully understood. An understanding of these will give knowledge of clock function and, across species, increase understanding of the ecological and evolutionary functions of circadian oscillators.
Additionally, identifying direct targets of PRR5, PRR7 and PRR9 that are not CCA1 and LHY will provide information about the molecular links from the PRRs to output genes like the flowering pathway and metabolism in mitochondria, which are CCA1-independent. | 1 | Biochemistry |
In the 1740s, Benjamin Huntsman found a means of melting blister steel, made by the cementation process, in crucibles. The resulting crucible steel, usually cast in ingots, was more homogeneous than blister steel. | 8 | Metallurgy |
A chemical clock (or clock reaction) is a complex mixture of reacting chemical compounds in which the onset of an observable property (discoloration or coloration) occurs after a predictable induction time due to the presence of clock species at a detectable amount.
In cases where one of the reagents has a visible color, crossing a concentration threshold can lead to an abrupt color change after a reproducible time lapse. | 7 | Physical Chemistry |
In electrochemistry, concentration polarization denotes the part of the polarization of an electrolytic cell resulting from changes in the electrolyte concentration due to the passage of current through the electrode/solution interface. Here polarization is understood as the shift of the electrochemical potential difference across the cell from its equilibrium value. When the term is used in this sense, it is equivalent to “concentration overpotential”.
the changes in concentration (emergence of concentration gradients in the solution adjacent to the electrode surface) is the difference in the rate of electrochemical reaction at the electrode and the rate of ion migration in the solution from/to the surface. When a chemical species participating in an electrochemical electrode reaction is in short supply, the concentration of this species at the surface decreases causing diffusion, which is added to the migration transport towards the surface in order to maintain the balance of consumption and delivery of that species. | 7 | Physical Chemistry |
The term self-neutralising acid sulfate soils has been used to refer to sulfidic material which does not become acidic upon oxidation due to the presence of alkaline materials (e.g., marine carbonates) - which neutralise acidity generated by the oxidation of sulfidic material.
The use of this term is discouraged as it can give the impression that the soil is not hazardous. Although the aerobic weathering of hyposulfidic material does not produce excess acidity, it typically generates a saline solution containing environmentally hazardous concentrations of metals and metalloids.Therefore, hyposulfidic material should be used instead of self-neutralising acid sulfate soil. | 9 | Geochemistry |
Many ylides may be depicted by a multiple bond form in a resonance structure, known as the ylene form, while the actual structure lies in between both forms:
The actual bonding picture of these types of ylides is strictly zwitterionic (the structure on the right) with the strong Coulombic attraction between the "onium" atom and the adjacent carbon accounting for the reduced bond length. Consequently, the carbon anion is trigonal pyramidal. | 0 | Organic Chemistry |
Photopigments are unstable pigments that undergo a chemical change when they absorb light. The term is generally applied to the non-protein chromophore moiety of photosensitive chromoproteins, such as the pigments involved in photosynthesis and photoreception. In medical terminology, "photopigment" commonly refers to the photoreceptor proteins of the retina. | 1 | Biochemistry |
A mixture of dimethyl ether and propane is used in some "freeze spray" preparations such as Dr. Scholl's Freeze Away. The mixture is stored in an aerosol spray type container at room temperature and drops to when dispensed. The mixture is often dispensed into a straw with a cotton-tipped swab. Similar products may use tetrafluoroethane or other substances. | 1 | Biochemistry |
Volatile organic compounds (VOCs) are organic compounds that have a high vapor pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a trait known as volatility.
VOCs are responsible for the odor of scents and perfumes as well as pollutants. VOCs play an important role in communication between animals and plants, e.g. attractants for pollinators, protection from predation, and even inter-plant interactions. Some VOCs are dangerous to human health or cause harm to the environment. Anthropogenic VOCs are regulated by law, especially indoors, where concentrations are the highest. Most VOCs are not acutely toxic, but may have long-term chronic health effects. Some VOCs have been used in pharmacy, while others are target of administrative controls because of their recreational use. | 0 | Organic Chemistry |
The first instance of a self-cleaning surface was created in 1995. Paz et al. created a transparent titanium dioxide (TiO) film that was used to coat glass and provide the ability for the glass to self-clean. The first commercial application of this self-cleaning surface, Pilkington Activ, was developed by Pilkington glass in 2001. This product implements a two-stage cleaning process. The first stage consists of photocatalysis of any fouling matter on the glass. This stage is followed by the glass becoming superhydrophilic and allowing water to wash away the catalyzed debris on the surface of the glass. Since the creation of self-cleaning glass, titanium dioxide has also been used to create self-cleaning nanoparticles that can be incorporated into other material surfaces to allow them to self-clean. | 7 | Physical Chemistry |
Knockouts are primarily used to understand the role of a specific gene or DNA region by comparing the knockout organism to a wildtype with a similar genetic background.
Knockout organisms are also used as screening tools in the development of drugs, to target specific biological processes or deficiencies by using a specific knockout, or to understand the mechanism of action of a drug by using a library of knockout organisms spanning the entire genome, such as in Saccharomyces cerevisiae. | 1 | Biochemistry |
MDI is commonly used in the manufacture of rigid foams and surface coating. Polyurethane foam boards are used in construction for insulation. TDI is commonly used in applications where flexible foams are used, such as furniture and bedding. Both MDI and TDI are used in the making of adhesives and sealants due to weather-resistant properties. Isocyanates, both MDI and TDI are widely used in as spraying applications of insulation due to the speed and flexibility of applications. Foams can be sprayed into structures and harden in place or retain some flexibility as required by the application. HDI is commonly utilized in high-performance surface-coating applications, including automotive paints. | 0 | Organic Chemistry |
A [2+2]-cycloaddition is a 4 electron process that brings together two components. Thus, by the above general WH rules, it is only allowed if the reaction is antarafacial with respect to exactly one component. This is the same conclusion reached with correlation diagrams in the section above.
A rare but stereochemically unambiguous example of a [2 + 2]-cycloaddition is shown on the right. The strain and steric properties of the trans double bond enables this generally kinetically unfavorable process. cis, trans-1,5-Cyclooctadiene is also believed to undergo dimerization via this mode. Ketenes are a large class of reactants favoring [2 + 2] cycloaddition with olefins. The MO analysis of ketene cycloaddition is rendered complicated and ambiguous by the simultaneous but independent interaction of the orthogonal orbitals of the ketene but may involve a [2 + 2] interaction as well. | 7 | Physical Chemistry |
Microbial corrosion, also called microbiologically influenced corrosion (MIC), microbially induced corrosion (MIC), or biocorrosion, is when microbes affect the electrochemical environment of the surface they are on. This usually involves building a biofilm, which can lead to either an increase in corrosion of the surface or, in a process called microbial corrosion inhibition, protect the surface from corrosion.
With every surface that is in some way exposed to the environment also exposed to microbes, microbial corrosion causes trillions of dollars in damage around the globe annually.
Microbes act by either producing byproducts from their cellular processes that corrode metals, or preventing normal corrosion inhibitors from functioning and leaving surfaces open to attack from other environmental factors. | 8 | Metallurgy |
Schoell received the 1995 AAPG Best Paper Award and was recognized by the American Association of Petroleum Geologists as authoring one of the top twenty most notable geology-related papers of the 1980s. Specifically, the AAPG recognized Schoell for his paper "Genetic Characterization of Natural Gasses" which describes how the correlation between C concentration, the variation of carbon and hydrogen isotopes in methane, and carbon isotope variation in ethane can be used to qualitatively characterize the composition of natural gasses.
In 2008, Schoell received the annual Alfred Treibs Award. This award is given on a yearly basis by the Geochemical Society in recognition of scientists whose research has made significant contributions to the understanding of geochemical processes. Schoell received this honour in response to his work with stable isotope analyses which revolutionized fossil fuel research and greenhouse gas tracing. | 9 | Geochemistry |
1st generation ATP tests are derived from hygiene monitoring uses where samples are relatively free of interferences. 2nd Generation tests are specifically designed for water, wastewater and industrial applications where, for the most part, samples contain a variety of components that can interfere with the ATP assay. | 2 | Environmental Chemistry |
The carbon-phosphorus triple bond in phosphaalkynes represents an exception to the so-called "double bond rule", which would suggest that phosphorus tends not to form multiple bonds to carbon, and the nature of bonding within phosphaalkynes has therefore attracted much interest from synthetic and theoretical chemists. For simple phosphaalkynes such as H-C≡P and Me-C≡P, the carbon-phosphorus bond length is known by microwave spectroscopy, and for certain more complex phosphaalkynes, these bond lengths are known from single-crystal X-ray diffraction experiments. These bond lengths can be compared to the theoretical bond length for a carbon-phosphorus triple bond predicted by Pekka Pyykkö of 1.54 Å. By bond length metrics, most structurally characterized alkyl and aryl substituted phosphaalkynes contain triple bonds between carbon and phosphorus, as their bond lengths are either equal to or less than the theoretical bond distance.
The carbon-phosphorus bond order in phosphaalkynes has also been the subject of computational inquiry, where quantum chemical calculations have been utilized to determine the nature of bonding in these molecules from first principles. In this context, natural bond orbital (NBO) theory has provided valuable insight into the bonding within these molecules. Lucas and coworkers have investigated the electronic structure of various substituted phosphaalkynes, including the cyaphide anion (C≡P), using NBO, natural resonance theory (NRT), and quantum theory of atoms in molecules (QTAIM) in an attempt to better describe the bonding in these molecules. For the simplest systems, C≡P and H-C≡P, NBO analysis suggests that the only relevant resonance structure is that in which there is a triple bond between carbon and phosphorus. For more complex molecules, such as Me-C≡P and (Me)C-C≡P, the triple bonded resonance structure is still the most relevant, but accounts for only some of the overall electron density within the molecule (81.5% and 72.1%, respectively). This is due to interactions between the two carbon-phosphorus pi-bonds and the C-H or C-C sigma-bonds of the substituents, which can be visualized by inspecting the C-P pi-bonding molecular orbitals in these molecules. | 0 | Organic Chemistry |
The overall metallic behavior of UPdAl, e.g. as deduced from the dc resistivity, is typical for a heavy-fermion material and can be explained as follows: incoherent Kondo scattering above approximately 80 K and coherent heavy-fermion state (in a Kondo lattice) at lower temperatures. Upon cooling below 14 K, UPdAl orders antiferromagnetically in a commensurate fashion (ordering wave vector (0,0,1/2)) and with a sizable ordered magnetic moment of approximately 0.85 µ per uranium atom, as determined from neutron scattering.
The metallic heavy-fermion state is characterized by a strongly enhanced effective mass, which is connected to a reduced Fermi velocity, which in turn brings about a strongly suppressed transport scattering rate. Indeed, for UPdAl optical Drude behavior with an extremely low scattering rate was observed at microwave frequencies. This is the slowest Drude relaxation observed for any three-dimensional metallic system so far. | 8 | Metallurgy |
Oxoferryl species are commonly proposed as intermediates in catalytic cycles, especially biological systems in which O activation is required. Diatomic oxygen has a high reduction potential (E = 1.23 V), but the first step required to harness this potential is a thermodynamically unfavorable one electron reduction E = -0.16 V. This reduction occurs in nature by the formation of a superoxide complex in which a reduced metal is oxidized by O. The product of this reaction is a peroxide radical that is more readily reactive. A widely applicable method for the generation of high-valent oxoferryl species is the oxidation with iodosobenzene: | 7 | Physical Chemistry |
The main tools used to collect bioaerosols are collection plates, electrostatic collectors, mass spectrometers, and impactors, other methods are used but are more experimental in nature.<nowiki/> Polycarbonate (PC) filters have had the most accurate bacterial sampling success when compared to other PC filter options. | 7 | Physical Chemistry |
Ultra-high-carbon steel has approximately 1.25–2.0% carbon content. Steels that can be tempered to great hardness. Used for special purposes such as (non-industrial-purpose) knives, axles, and punches. Most steels with more than 2.5% carbon content are made using powder metallurgy. | 8 | Metallurgy |
The concept of Voronoi decomposition was investigated by Peter Gustav Lejeune Dirichlet, leading to the name Dirichlet domain. Further contributions were made from Evgraf Fedorov, (Fedorov parallelohedron), Georgy Voronoy (Voronoi polyhedron), and Paul Niggli (Wirkungsbereich).
The application to condensed matter physics was first proposed by Eugene Wigner and Frederick Seitz in a 1933 paper, where it was used to solve the Schrödinger equation for free electrons in elemental sodium. They approximated the shape of the Wigner–Seitz cell in sodium, which is a truncated octahedron, as a sphere of equal volume, and solved the Schrödinger equation exactly using periodic boundary conditions, which require at the surface of the sphere. A similar calculation which also accounted for the non-spherical nature of the Wigner–Seitz cell was performed later by John C. Slater.
There are only five topologically distinct polyhedra which tile three-dimensional space, . These are referred to as the parallelohedra. They are the subject of mathematical interest, such as in higher dimensions. These five parallelohedra can be used to classify the three dimensional lattices using the concept of a projective plane, as suggested by John Horton Conway and Neil Sloane. However, while a topological classification considers any affine transformation to lead to an identical class, a more specific classification leads to 24 distinct classes of voronoi polyhedra with parallel edges which tile space. For example, the rectangular cuboid, right square prism, and cube belong to the same topological class, but are distinguished by different ratios of their sides. This classification of the 24 types of voronoi polyhedra for Bravais lattices was first laid out by Boris Delaunay. | 3 | Analytical Chemistry |
The common-ion effect is the effect of decreased solubility of one salt when another salt that has an ion in common with it is also present. For example, the solubility of silver chloride, AgCl, is lowered when sodium chloride, a source of the common ion chloride, is added to a suspension of AgCl in water.
The solubility, S, in the absence of a common ion can be calculated as follows. The concentrations [Ag] and [Cl] are equal because one mole of AgCl would dissociate into one mole of Ag and one mole of Cl. Let the concentration of [Ag(aq)] be denoted by x. Then
K for AgCl is equal to at 25 °C, so the solubility is .
Now suppose that sodium chloride is also present, at a concentration of 0.01 mol dm = 0.01 M. The solubility, ignoring any possible effect of the sodium ions, is now calculated by
This is a quadratic equation in x, which is also equal to the solubility.
In the case of silver chloride, x is very much smaller than 0.01 M x, so the first term can be ignored. Therefore
a considerable reduction from . In gravimetric analysis for silver, the reduction in solubility due to the common ion effect is used to ensure "complete" precipitation of AgCl. | 7 | Physical Chemistry |
Because the kinetic energy of the emitted electrons is exactly the energy of the incident photon minus the energy of the electron's binding within an atom, molecule or solid, the binding energy can be determined by shining a monochromatic X-ray or UV light of a known energy and measuring the kinetic energies of the photoelectrons. The distribution of electron energies is valuable for studying quantum properties of these systems. It can also be used to determine the elemental composition of the samples. For solids, the kinetic energy and emission angle distribution of the photoelectrons is measured for the complete determination of the electronic band structure in terms of the allowed binding energies and momenta of the electrons. Modern instruments for angle-resolved photoemission spectroscopy are capable of measuring these quantities with a precision better than 1 meV and 0.1°.
Photoelectron spectroscopy measurements are usually performed in a high-vacuum environment, because the electrons would be scattered by gas molecules if they were present. However, some companies are now selling products that allow photoemission in air. The light source can be a laser, a discharge tube, or a synchrotron radiation source.
The concentric hemispherical analyzer is a typical electron energy analyzer. It uses an electric field between two hemispheres to change (disperse) the trajectories of incident electrons depending on their kinetic energies. | 7 | Physical Chemistry |
Wheal Maid (also Wheal Maiden) is a former mine in the Camborne-Redruth-St Day Mining District, 1.5 km east of St Day.
Between 1800 and 1840, profits are said to have been up to £200,000. In 1852, the mine was amalgamated with Poldice Mine and Carharrack Mine and worked as St Day United mine. Throughout the 1970s and 1980s, the mine site was turned into large lagoons and used as a tip for two other nearby mines: Mount Wellington and Wheal Jane.
There were suggestions that the mine could be used as a landfill site for rubbish imported from New York and a power plant that would produce up to 40 megawatts of electricity; the concept was opposed by local residents and by Cornwall County Council, with Doris Ansari, the chair of the council's planning committee, saying that the idea "[did] not seem right for Cornwall".
The site was bought from Carnon Enterprises by Gwennap District Council for a price of £1 in 2002. An investigation by the Environment Agency that concluded in 2007 found that soil near the mine had high levels of arsenic, copper and zinc contamination and by 2012, it was deemed too hazardous for human activity.
The mine gains attention during dry spells when the lagoons dry up and leaving brightly coloured stains on the pit banks and bed. | 2 | Environmental Chemistry |
In 2007, the European Commission gave authorization for the marketing of trabectedin, under the trade name Yondelis, "for the treatment of patients with advanced soft tissue sarcoma, after failure of anthracyclines and ifosfamide, or who are unsuited to receive these agents". The European Medicine Agency's evaluating committee, the Committee for Medicinal Products for Human Use (CHMP), observed that trabectedin had not been evaluated in an adequately designed and analyzed randomized controlled trial against current best care, and that the clinical efficacy data were mainly based on patients with liposarcoma and leiomyosarcoma. However, the pivotal study did show a significant difference between two different trabectedin treatment regimens, and due to the rarity of the disease, the CHMP considered that marketing authorization could be granted under exceptional circumstances. As part of the approval PharmaMar agreed to conduct a further trial to identify whether any specific chromosomal translocations could be used to predict responsiveness to trabectedin.
Trabectedin is also approved in South Korea and Russia.
In 2015, (after a phase III study comparing trabectedin with dacarbazine), the US FDA approved trabectedin (Yondelis) for the treatment of liposarcoma and leiomyosarcoma that is either unresectable or has metastasized. Patients must have received prior chemotherapy with an anthracycline. | 0 | Organic Chemistry |
Symptoms following bee sting may include:
*Local effects: burning or stinging pain, swelling, redness.
*Severe systemic reactions: swelling of the tongue and throat, difficulty breathing, and shock.
*Development of optic neuritis and atrophy.
*Atrial fibrillation, cerebral infarction, acute myocardial infarction, Fisher's syndrome, acute inflammatory polyradiculopathy (Guillain–Barré syndrome), claw hand (through a central action of apamin on the spinal cord and a peripheral action in the form of median and ulnar neuritis, causing spasms of the long flexors in the forearm).
Patients poisoned with bee venom can be treated with anti-inflammatory medication, antihistamines and oral prednisolone.
Apamin is an element in bee venom. You can come into contact with apamin through bee venom, so the symptoms that are known are not caused by apamin directly, but by the venom as a whole. Apamin is the only neurotoxin acting purely on the central nervous system. The symptoms of apamin toxicity are not well known, because people are not easily exposed to the toxin alone.
Through research about the neurotoxicity of apamin some symptoms were discovered. In mice, the injection of apamin produces convulsions and long-lasting spinal spasticity. Also, it is known that the polysynaptic spinal reflexes are disinhibited in cats. Polysynaptic reflex is a reflex action that transfers an impulse from a sensory neuron to a motor neuron via an interneuron in the spinal cord. In rats, apamin was found to cause tremor and ataxia, as well as dramatic haemorrhagic effects in the lungs.
Furthermore, apamin has been found to be 1000 times more efficient when applied into the ventricular system instead of the peripheral nervous system. The ventricular system is a set of structures in the brain containing cerebrospinal fluid. The peripheral nervous system contains the nerves and ganglia outside of the brain and spinal cord. This difference in efficiency can easily be explained. Apamin binds to the SK channels, which differ slightly in different tissues. So apamin binding is probably stronger in SK channels in the ventricular system than in other tissues. | 1 | Biochemistry |
In the mechanical stream of thinking about a process of transfer of energy between two bodies or closed systems, heat transferred is defined as a residual amount of energy transferred after the energy transferred as work has been determined, assuming for the calculation the law of conservation of energy, without reference to the concept of temperature. There are five main elements of the underlying theory.
*The existence of states of thermodynamic equilibrium, determinable by precisely one (called the non-deformation variable) more variable of state than the number of independent work (deformation) variables.
*That a state of internal thermodynamic equilibrium of a body have a well defined internal energy, that is postulated by the first law of thermodynamics.
*The universality of the law of conservation of energy.
*The recognition of work as a form of energy transfer.
*The universal irreversibility of natural processes.
*The existence of adiabatic enclosures.
*The existence of walls permeable only to heat.
Axiomatic presentations of this stream of thinking vary slightly, but they intend to avoid the notions of heat and of temperature in their axioms. It is essential to this stream of thinking that heat is not presupposed as being measurable by calorimetry. It is essential to this stream of thinking that, for the specification of the thermodynamic state of a body or closed system, in addition to the variables of state called deformation variables, there be precisely one extra real-number-valued variable of state, called the non-deformation variable, though it should not be axiomatically recognized as an empirical temperature, even though it satisfies the criteria for one. | 7 | Physical Chemistry |
Bioasphalt is an asphalt alternative made from non-petroleum based renewable resources.
These sources include sugar, molasses and rice, corn and potato starches, natural tree and gum resins, natural latex rubber and vegetable oils, lignin, cellulose, palm oil waste, coconut waste, peanut oil waste, canola oil waste, dried sewerage effluent and so on. Bitumen can also be made from waste vacuum tower bottoms produced in the process of cleaning used motor oils, which are normally burned or dumped into land fills.
Non-petroleum based bitumen binders can be colored, which can reduce the temperatures of road surfaces and reduce the Urban heat islands. | 7 | Physical Chemistry |
Sulfide is an angular functional group, the C–S–C angle approaching 90° The C–S bonds are about 180 pm.
For the prototype, dimethylsulfide, the C-S-C angles is 99°, which is smaller than the C-O-C angle in ether (~110°). The C-S distance in dimethylsulfide is 1.81 Å.
Sulfides are characterized by their strong odors, which are similar to thiol odor. This odor limits the applications of volatile sulfides. In terms of their physical properties they resemble ethers, but are less volatile, higher melting, and less hydrophilic. These properties follow from the polarizability of the divalent sulfur center, which is greater than that for oxygen in ethers. | 0 | Organic Chemistry |
Recently PPARGC1A has been implicated as a potential therapy for Parkinson's disease conferring protective effects on mitochondrial metabolism.
Moreover, brain-specific isoforms of PGC-1alpha have recently been identified which are likely to play a role in other neurodegenerative disorders such as Huntington's disease and amyotrophic lateral sclerosis.
Massage therapy appears to increase the amount of PGC-1α, which leads to the production of new mitochondria.
PGC-1α and beta has furthermore been implicated in polarization to anti-inflammatory M2 macrophages by interaction with PPAR-γ with upstream activation of STAT6. An independent study confirmed the effect of PGC-1 on polarisation of macrophages towards M2 via STAT6/PPAR gamma and furthermore demonstrated that PGC-1 inhibits proinflammatory cytokine production.
PGC-1α has been recently proposed to be responsible for β-aminoisobutyric acid secretion by exercising muscles. The effect of β-aminoisobutyric acid in white fat includes the activation of thermogenic genes that prompt the browning of white adipose tissue and the consequent increase of background metabolism. Hence, the β-aminoisobutyric acid could act as a messenger molecule of PGC-1α and explain the effects of PGC-1α increase in other tissues such as white fat.
PGC-1α increases BNP expression by coactivating ERRα and / or AP1. Subsequently, BNP induces a chemokine cocktail in muscle fibers and activates macrophages in a local paracrine manner, which can then contribute to enhancing the repair and regeneration potential of trained muscles.
Most studies reporting effects of PGC-1α on physiological functions have used mouse models in which the PGC-1α gene is either knocked out or overexpressed from conception. However, some of the proposed effects of PGC-1α have been questioned by studies using inducible knockout technology to remove the PGC-1α gene only in adult mice. For example, two independent studies have shown that adult expression of PGC-1α is not required for improved mitochondrial function after exercise training. This suggests that some of the reported effects of PGC-1α are likely to occur only in the developmental stage. | 1 | Biochemistry |
Sedoheptulose 7-phosphate is an intermediate in the pentose phosphate pathway.
It is formed by transketolase and acted upon by transaldolase.
Sedoheptulokinase is an enzyme that uses sedoheptulose and ATP to produce ADP and sedoheptulose 7-phosphate.
Sedoheptulose-bisphosphatase is an enzyme that uses sedoheptulose 1,7-bisphosphate and HO to produce sedoheptulose 7-phosphate and phosphate. | 1 | Biochemistry |
The immune system plays an important role in monitoring and destroying abnormal or cancerous cells. Telomere extension may affect the immune system's ability to recognize and eliminate cells with long telomeres, potentially compromising immune surveillance. It is very important to ensure the ability of the immune system to effectively identify and fight against pathogens and abnormal cells. | 1 | Biochemistry |
Before it was flooded, Norşuntepe was located on the Altınova Plain near the mouth of the Murat River (downstream from the town of Palu, Elazığ). It is now partially submerged by the reservoir created by the Keban Dam; its top is still above the water level. The site consists of a central hill or "acropolis" measuring and high, making it the largest tell in the area. The central hill is surrounded by lower terraces encompassing an area of . | 8 | Metallurgy |
The journal is abstracted and indexed in:
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According to the Journal Citation Reports, the journal has a 2020 impact factor of 4.105. | 0 | Organic Chemistry |
Simeon Chituru Achinewhu (born 15 August, 1946) is a Nigerian food and nutrition biochemist, scholar and university administrator who served as the past president-general of Ogbakor Ikwerre Socio-cultural Organisation Worldwide. He was vice–chancellor of River State University (formerly Rivers State University of Science and Technology), from October 2000 until May 2007. In 2005 he was named the most research active vice-chancellor in the Nigerian university system. | 1 | Biochemistry |
Primary (direct) immunofluorescence (DIF) uses a single antibody, conjugated to a fluorophore. The antibody recognizes the target molecule (antigen) and binds to a specific region, called the epitope. The attached fluorophore can be detected via fluorescent microscopy, which, depending on the type of fluorophore, will emit a specific wavelength of light once excited.
The direct attachment of the fluorophore to the antibody reduces the number of steps in the sample preparation procedure, saving time and reducing non-specific background signal during analysis. This also limits the possibility of antibody cross-reactivity, and possible mistakes throughout the process. One disadvantage of DIF is the limited number of antibodies that can bind to the antigen. This limitation may reduce sensitivity to the technique. When the target protein is available in only small concentrations, a better approach would be secondary IF, which is considered to be more sensitive than DIF when compared to Secondary (Indirect) Immunofluorescence. | 1 | Biochemistry |
With Tamás Turányi, Tomlin is coauthor of the book Analysis of Kinetic Reaction Mechanisms (Springer, 2014). | 7 | Physical Chemistry |
Despite formal recommendation to the contrary, the term partition coefficient remains the predominantly used term in the scientific literature.
In contrast, the IUPAC recommends that the title term no longer be used, rather, that it be replaced with more specific terms. For example, partition constant, defined as
where K is the process equilibrium constant, [A] represents the concentration of solute A being tested, and "org" and "aq" refer to the organic and aqueous phases respectively. The IUPAC further recommends "partition ratio" for cases where transfer activity coefficients can be determined, and "distribution ratio" for the ratio of total analytical concentrations of a solute between phases, regardless of chemical form. | 7 | Physical Chemistry |
Directing edits to correct mutated sequences was first proposed and demonstrated in 1995. This initial work used synthetic RNA antisense oligonucleotides complementary to a pre-mature stop codon mutation in a dystrophin sequence to activate A-to-I editing of the stop codon to a read through codon in a model xenopus cell system. While this also led to nearby inadvertent A-to-I transitions, A to I (read as G) transitions can correct all three stop codons, but cannot create a stop codon. Therefore, the changes led >25% correction of the targeted stop codon with read through to a downstream luciferase reporter sequence. Follow on work by Rosenthal achieved editing of mutated mRNA sequence in mammalian cell culture by directing an oligonucleotide linked to a cytidine deaminase to correct a mutated cystic fibrosis sequence. More recently, CRISPR-Cas13 fused to deaminases has been employed to direct mRNA editing.
In 2022, therapeutic RNA editing for Cas7-11 was reported. It enables sufficiently targeted cuts and an early version of it was used for in vitro editing in 2021. | 1 | Biochemistry |
Usually, an enzyme molecule has only one active site, and the active site fits with one specific type of substrate. An active site contains a binding site that binds the substrate and orients it for catalysis. The orientation of the substrate and the close proximity between it and the active site is so important that in some cases the enzyme can still function properly even though all other parts are mutated and lose function.
Initially, the interaction between the active site and the substrate is non-covalent and transient. There are four important types of interaction that hold the substrate in a defined orientation and form an enzyme-substrate complex (ES complex): hydrogen bonds, van der Waals interactions, hydrophobic interactions and electrostatic force interactions. The charge distribution on the substrate and active site must be complementary, which means all positive and negative charges must be cancelled out. Otherwise, there will be a repulsive force pushing them apart. The active site usually contains non-polar amino acids, although sometimes polar amino acids may also occur. The binding of substrate to the binding site requires at least three contact points in order to achieve stereo-, regio-, and enantioselectivity. For example, alcohol dehydrogenase which catalyses the transfer of a hydride ion from ethanol to NAD interacts with the substrate methyl group, hydroxyl group and the pro-(R) hydrogen that will be abstracted during the reaction.
In order to exert their function, enzymes need to assume their correct protein fold (native fold) and tertiary structure. To maintain this defined three-dimensional structure, proteins rely on various types of interactions between their amino acid residues. If these interactions are interfered with, for example by extreme pH values, high temperature or high ion concentrations, this will cause the enzyme to denature and lose its catalytic activity.
A tighter fit between an active site and the substrate molecule is believed to increase the efficiency of a reaction. If the tightness between the active site of DNA polymerase and its substrate is increased, the fidelity, which means the correct rate of DNA replication will also increase. Most enzymes have deeply buried active sites, which can be accessed by a substrate via access channels.
There are three proposed models of how enzymes fit their specific substrate: the lock and key model, the induced fit model, and the conformational selection model. The latter two are not mutually exclusive: conformational selection can be followed by a change in the enzyme's shape. Additionally, a protein may not wholly follow either model. Amino acids at the binding site of ubiquitin generally follow the induced fit model, whereas the rest of the protein generally adheres to conformational selection. Factors such as temperature likely influences the pathway taken during binding, with higher temperatures predicted to increase the importance of conformational selection and decrease that of induced fit. | 1 | Biochemistry |
Aptamers were originally discovered in 1990 when Lary Gold and Craig Tuerk utilized a method of directed evolution known as SELEX to isolate a small single stranded RNA molecule that was capable of binding to T4 bacteriophage DNA polymerase. Additionally, the term “aptamer” was coined by Andrew Ellington, who worked with Jack Szostak to select an RNA aptamer that was capable of tight binding to certain organic dye molecules. The term itself is a conglomeration of the Latin “aptus” or “to fit” and the Greek “meros” or “part."
RNA aptamers are not so much “created” as “selected.” To develop an RNA aptamer capable of selective binding to a molecular target, a method known as Systematic Evolution of Ligands by EXponential Enrichment (SELEX) is used to isolate a unique RNA aptamer from a pool of ~10^13 to 10^16 different aptamers, otherwise known as a library. The library of potential aptamer oligonucleotides is then incubated with a non-target species so as to remove aptamers that exhibit non-specific binding. After subsequent removal of the non-specific aptamers, the remaining library members are then exposed to the desired target, which can be a protein, peptide, cell type, or even an organ (in the case of live animal-based SELEX). From there, the RNA aptamers which were bound to the target are transcribed to cDNA which then is amplified through PCR, and the PCR products are then re-transcribed to RNA. These new RNA transcripts are then used to repeat the selection cycle many times, thus eventually producing a homogeneous pool of RNA aptamers capable of highly specific, high-affinity target binding. | 1 | Biochemistry |
In vitro fertilization involves removing eggs from a woman, collecting sperm from a man, fertilizing the egg with the sperm, allowing the fertilized egg to form a blastocyst, and then transferring the blastocyst into the uterus. MRT involves an additional egg from a third person, and manipulation of both the recipient egg and the donor egg.
As of 2016 there were three MRT techniques in use: maternal spindle transfer (MST); pronuclear transfer (PNT); and the newest technique, polar body transfer (PBT). The original technique, in which mitochondria-containing cytoplasm taken from a donor egg is simply injected into the recipient egg, is no longer used.
In maternal spindle transfer, an oocyte is removed from the recipient, and when it is in the metaphase II stage of cell division, the spindle-chromosome complex is removed; some of the cytoplasm comes with it, so some mitochondria are likely to be included. The spindle-chromosome complex is inserted into a donor oocyte from which the nucleus has already been removed. This egg is fertilized with sperm and allowed to form a blastocyst, which can then be investigated with preimplantation genetic diagnosis to check for mitochondrial mutations, prior to being implanted in the recipient's uterus.
In pronuclear transfer, an oocyte is removed from the recipient and fertilized with sperm. The donor oocyte is fertilized with sperm from the same person. The male and female pronuclei are removed from each fertilized egg prior to their fusing, and the pronuclei from the recipients fertilized egg are inserted into the fertilized egg from the donor. As with MST, a small amount of cytoplasm from the recipient egg may be transferred, and as with MST, the fertilized egg is allowed to form a blastocyst, which can then be investigated with preimplantation genetic diagnosis to check for mitochondrial mutations before being implanted in the recipients uterus.
In polar body transfer, a polar body (a small cell with very little cytoplasm that is created when an egg cell divides) from the recipient is used in its entirety, instead of using nuclear material extracted from the recipients normal egg; this can be used in either MST or PNT. This technique was first published in 2014 and as of 2015 it had not been consistently replicated, but is considered promising as there is a greatly reduced chance for transmitting mitochondria from the recipient because polar bodies contain very few mitochondria, and it does not involve extracting material from the recipients egg. | 1 | Biochemistry |
Applying the ideas above, chirality of organometallic compounds can be deduced as well with this technique. Each chiral compound has its own unique properties and binding mechanisms that are comparable to each other, which leads to differences in thermodynamic properties. By binding chiral solutions in a binding site can deduce the type of chirality and depending on the purpose, which chiral compound is more suitable for binding. | 7 | Physical Chemistry |
Soderholm's more recent projects use machine learning to understand the influence of complex molecular structuring in solutions, in connection with low-energy processes for separation of f-block elements from complex mixtures. | 7 | Physical Chemistry |
5-Formiminotetrahydrofolate is an intermediate in the catabolism of histidine. It is produced by glutamate formimidoyltransferase and then converted into 5,10-methenyltetrahydrofolate by formiminotransferase cyclodeaminase. | 1 | Biochemistry |
A common application of block copolymers is to develop thermoplastic elastomers (TPEs). Early commercial TPEs were developed from polyurethranes (TPUs), consisting of alternating soft segments and hard segments, and are used in automotive bumpers and snowmobile treads. Styrenic TPEs entered the market later, and are used in footwear, bitumen modification, thermoplastic blending, adhesives, and cable insulation and gaskets. Modifying the linkages between the blocks resulted in newer TPEs based on polyesters (TPES) and polyamides (TPAs), used in hose tubing, sport goods, and automotive components.
Amphiphilic block copolymers have the ability to form micelles and nanoparticles. Due to this property, amphiphilic block copolymers have garnered much attention in research on vehicles for drug delivery. Similarly, amphiphilic block copolymers can be used for the removal of organic contaminants from water either through micelle formation or film preparation. | 7 | Physical Chemistry |
Dicarbollides are obtained by base-degradation of 12-vertex dicarboranes. This degradation of the ortho derivative has been most heavily studied. The conversion is conducted in two-steps, first "deboronation" and second deprotonation:
:CBH + NaOEt + 2 EtOH → NaCBH + H + B(OEt)
:NaCBH + NaH → NaCBH + H
The dianion derived from dicarboranes, [CBH], are nido clusters. Three isomers exist. Most commonly studies is the 7,8-isomer, with two adjacent carbon centers on the rim. 7,9- has non-adjacent carbon centers on the rim. It is derived by degradation of meta-. 2,9- has only one carbon center on the rim. It is derived by degradation of para-. | 7 | Physical Chemistry |
Isomerization is the process by which one molecule is transformed into another molecule that has exactly the same atoms, but the atoms are rearranged. In some molecules and under some conditions, isomerization occurs spontaneously. Many isomers are equal or roughly equal in bond energy, and so exist in roughly equal amounts, provided that they can interconvert relatively freely, that is the energy barrier between the two isomers is not too high. When the isomerization occurs intramolecularly, it is considered a rearrangement reaction.
An example of an organometallic isomerization is the production of decaphenylferrocene, [(η-CPh)Fe] from its linkage isomer.
;Synthesis of fumaric acid
Industrial synthesis of fumaric acid proceeds via the cis-trans isomerization of maleic acid:
Topoisomerases are enzymes that can cut and reform circular DNA and thus change its topology. | 4 | Stereochemistry |
*Spark plug
*Water cooled barrel
*Nitrogen inlet valve
*Fuel inlet valve
*Oxygen inlet valve
*Powder feedstock inlet valve | 8 | Metallurgy |
There are also three structural isomers of the hydrocarbon :
In two of the isomers, the three carbon atoms are connected in an open chain, but in one of them (propadiene or allene; I) the carbons are connected by two double bonds, while in the other (propyne or methylacetylene; II) they are connected by a single bond and a triple bond. In the third isomer (cyclopropene; III) the three carbons are connected into a ring by two single bonds and a double bond. In all three, the remaining valences of the carbon atoms are satisfied by the four hydrogens.
Again, note that there is only one structural isomer with a triple bond, because the other possible placement of that bond is just drawing the three carbons in a different order. For the same reason, there is only one cyclopropene, not three. | 4 | Stereochemistry |
Isotactic polymers are composed of isotactic macromolecules (IUPAC definition). In isotactic macromolecules all the substituents are located on the same side of the macromolecular backbone. An isotactic macromolecule consists of 100% meso diads. Polypropylene formed by Ziegler–Natta catalysis is an isotactic polymer. Isotactic polymers are usually semicrystalline and often form a helix configuration. | 4 | Stereochemistry |
These processes are the physicochemical phenomena and reactions caused by movement of hydrothermal water within the crust, often as a consequence of magmatic intrusion or tectonic upheavals. The foundations of hydrothermal processes are the source-transport-trap mechanism.
Sources of hydrothermal solutions include seawater and meteoric water circulating through fractured rock, formational brines (water trapped within sediments at deposition), and metamorphic fluids created by dehydration of hydrous minerals during metamorphism.
Metal sources may include a plethora of rocks. However most metals of economic importance are carried as trace elements within rock-forming minerals, and so may be liberated by hydrothermal processes. This happens because of:
*incompatibility of the metal with its host mineral, for example zinc in calcite, which favours aqueous fluids in contact with the host mineral during diagenesis.
*solubility of the host mineral within nascent hydrothermal solutions in the source rocks, for example mineral salts (halite), carbonates (cerussite), phosphates (monazite and thorianite), and sulfates (barite)
*elevated temperatures causing decomposition reactions of minerals
Transport by hydrothermal solutions usually requires a salt or other soluble species which can form a metal-bearing complex. These metal-bearing complexes facilitate transport of metals within aqueous solutions, generally as hydroxides, but also by processes similar to chelation.
This process is especially well understood in gold metallogeny where various thiosulfate, chloride, and other gold-carrying chemical complexes (notably tellurium-chloride/sulfate or antimony-chloride/sulfate). The majority of metal deposits formed by hydrothermal processes include sulfide minerals, indicating sulfur is an important metal-carrying complex. | 9 | Geochemistry |
A 2009 statement from the ASRM found no persuasive evidence that children are harmed or disadvantaged solely by being raised by single parents, unmarried parents, or homosexual parents. It did not support restricting access to assisted reproductive technologies on the basis of a prospective parents marital status or sexual orientation. A 2018 study found that childrens psychological well-being did not differ when raised by either same-sex parents or heterosexual parents, even finding that psychological well-being was better amongst children raised by same-sex parents.
Ethical concerns include reproductive rights, the welfare of offspring, nondiscrimination against unmarried individuals, homosexual, and professional autonomy.
A controversy in California focused on the question of whether physicians opposed to same-sex relationships should be required to perform IVF for a lesbian couple. Guadalupe T. Benitez, a lesbian medical assistant from San Diego, sued doctors Christine Brody and Douglas Fenton of the North Coast Womans Care Medical Group after Brody told her that she had "religious-based objections to treating her and homosexuals in general to help them conceive children by artificial insemination," and Fenton refused to authorise a refill of her prescription for the fertility drug Clomid on the same grounds. The California Medical Association had initially sided with Brody and Fenton, but the case, North Coast Womens Care Medical Group v. Superior Court, was decided unanimously by the California State Supreme Court in favour of Benitez on 19 August 2008.
Nadya Suleman came to international attention after having twelve embryos implanted, eight of which survived, resulting in eight newborns being added to her existing six-child family. The Medical Board of California sought to have fertility doctor Michael Kamrava, who treated Suleman, stripped of his licence. State officials allege that performing Sulemans procedure is evidence of unreasonable judgment, substandard care, and a lack of concern for the eight children she would conceive and the six she was already struggling to raise. On 1 June 2011 the Medical Board issued a ruling that Kamravas medical licence be revoked effective 1 July 2011. | 1 | Biochemistry |
The Faraday-efficiency effect refers to the potential for misinterpretation of data from experiments in electrochemistry through failure to take into account a Faraday efficiency of less than 100 percent. | 7 | Physical Chemistry |
Orientational anisotropy takes the form of a difference in both diffusion rates and mechanisms at the various surface orientations of a given material. For a given crystalline material each Miller Index plane may display unique diffusion phenomena. Close packed surfaces such as the fcc (111) tend to have higher diffusion rates than the correspondingly more "open" faces of the same material such as fcc (100).
Directional anisotropy refers to a difference in diffusion mechanism or rate in a particular direction on a given crystallographic plane. These differences may be a result of either anisotropy in the surface lattice (e.g. a rectangular lattice) or the presence of steps on a surface. One of the more dramatic examples of directional anisotropy is the diffusion of adatoms on channeled surfaces such as fcc (110), where diffusion along the channel is much faster than diffusion across the channel. | 7 | Physical Chemistry |
As with all airborne particulates, wood dust particle sizes are classified with regard to effect on the human respiratory system. For this classification, the unit for measurement of particle sizes is the micrometre or micron (μm), where 1 micrometre = 1 micron. Particles below 50 μm are not normally visible to the naked human eye. Particles of concern for human respiratory health are those <100 μm (where the symbol < means ‘less than’).
Zhang (2004) has defined the size of indoor particulates according to respiratory fraction:
Particles which precipitate in the vicinity of the mouth and eyes, and get into the organism, are defined as the inhalable fraction, that is total dust. Smaller fractions, penetrating into the non-cartilage respiratory tract, are defined as respirable dust. Dust emitted in the wood industry is characterized by the dimensional disintegration of particles up to 5 μm, and that
is why they precipitate mostly in the nasal cavity, increasing the risk of cancer of the upper respiratory tract. | 2 | Environmental Chemistry |
Isotope effect is observed when molecules containing heavier isotopes of the same atoms (for example, deuterium instead of hydrogen) are engaged in a chemical reaction at a slower rate. Deuterium-reinforced lipids can be used for the protection of living cells by slowing the chain reaction of lipid peroxidation. The lipid bilayer of the cell and organelle membranes contain polyunsaturated fatty acids (PUFA) are key components of cell and organelle membranes. Any process that either increases oxidation of PUFAs or hinders their ability to be replaced can lead to serious disease. Correspondingly, drugs that stop the chain reaction of lipid peroxidation have preventive and therapeutic potential. | 7 | Physical Chemistry |
Knowledge of bioaerosols has shaped our understanding of microorganisms and the differentiation between microbes, including airborne pathogens. In the 1970s, a breakthrough occurred in atmospheric physics and microbiology when ice nucleating bacteria were identified.
The highest concentration of bioaerosols is near the Earth’s surface in the PBL. Here wind turbulence causes vertical mixing, bringing particles from the ground into the atmosphere. Bioaerosols introduced to the atmosphere can form clouds, which are then blown to other geographic locations and precipitate out as rain, hail, or snow. Increased levels of bioaerosols have been observed in rain forests during and after rain events. Bacteria and phytoplankton from marine environments have been linked to cloud formation.
However, for this same reason, bioaerosols cannot be transported long distances in the PBL since the clouds will eventually precipitate them out. Furthermore, it would take additional turbulence or convection at the upper limits of the PBL to inject bioaerosols into the troposphere where they may transported larger distances as part of tropospheric flow. This limits the concentration of bioaerosols at these altitudes.
Cloud droplets, ice crystals, and precipitation use bioaerosols as a nucleus where water or crystals can form or hold onto their surface. These interactions show that air particles can change the hydrological cycle, weather conditions, and weathering around the world. Those changes can lead to effects such as desertification which is magnified by climate shifts. Bioaerosols also intermix when pristine air and smog meet, changing visibility and/or air quality. | 7 | Physical Chemistry |
Aminoallyl nucleosides can be synthesized via Heck coupling as shown in the image below.
In the image above, on the left is a modified nucleoside with an iodine (the iodine is added via electrophilic halogenation) in the fifth carbon in the pyrimidine ring. Its formation can be associated with a reaction with an allylamine and various reagents via heck coupling are able to remove the halogen group from the base and add the allylamine to become the aminoallyl nucleoside shown on the right. The product on the right is then used to in molecular biology in RNA synthesis.
Other reactions include using a single pot synthesis with other halogens. | 1 | Biochemistry |
POC is decomposed by a series of microbe-driven processes, such as methanogenesis and sulfate reduction, before burial in the seafloor. Degradation of POC also results in microbial methane production which is the main gas hydrate on the continental margins. Lignin and pollen are inherently resistant to degradation, and some studies show that inorganic matrices may also protect organic matter. Preservation rates of organic matter depend on other interdependent variables that vary nonlinearly in time and space. Although organic matter breakdown occurs rapidly in the presence of oxygen, microbes utilizing a variety of chemical species (via redox gradients) can degrade organic matter in anoxic sediments. The burial depth at which degradation halts depends upon the sedimentation rate, the relative abundance of organic matter in the sediment, the type of organic matter being buried, and innumerable other variables. While decomposition of organic matter can occur in anoxic sediments when bacteria use oxidants other than oxygen (nitrate, sulfate, Fe), decomposition tends to end short of complete mineralization. This occurs because of preferential decomposition of labile molecules over refractile molecules. | 9 | Geochemistry |
The manganese-containing salen complex catalyzes the asymmetric epoxidation of alkenes. In the hydrolytic kinetic resolution technique, a racemic mixture of epoxides may be separated by selectively hydrolyzing one enantiomer, catalyzed by the analogous cobalt(III) complex. In subsequent work, chromium(III) and cobalt(III) salen complexes catalyze the reaction of carbon dioxide and epoxides to give polycarbonates. | 0 | Organic Chemistry |
#Isolate the fly genome.
#Undergo a light digest (using an enzyme [enzyme 1] known to cut in the boundary between the reporter gene and the E. coli reporter gene and plasmid sequences), giving fragments of a few kilobases, a few with the E. coli reporter, the plasmid sequences and its flanking DNA.
#Self ligate the digest (low DNA concentration to ensure self ligation) giving a selection of circular DNA fragments, a few with the E. coli reporter, the plasmid sequences and its flanking DNA.
#Insert the plasmids into E. coli cells (e.g. by electroporation).
#Select plasmids for the E. coli selectable marker gene. Only successful inserts of plasmids with the plasmid housekeeping sequences will express this gene.
#The gene can be cloned for further analysis. | 1 | Biochemistry |
Manganese like magnesium plays a crucial role as a co-factor in various enzymes though its concentration is noticeably lower than the other. Enzymes that use manganese as a co-factor are known as "manganoproteins." These proteins include enzymes, like oxidoreductases, transferases and hydrolases, which are necessary for metabolic functions and antioxidant responses. Manganese plays a significant role in host defense, blood clotting, reproduction, digestion and various other functions in the body. In particular, when concerning host defense, manganese acts as a preventative measure for oxidative stress by destroying free radicals which are ions that have an unpaired electron in their outer shells. | 1 | Biochemistry |
The worm-like chain model (WLC) takes the energy required to bend a molecule into account. The variables are the same except that , the persistence length, replaces . Then, the force follows this equation:
Therefore, when there is no distance between chain ends (r=0), the force required to do so is zero, and to fully extend the polymer chain (), an infinite force is required, which is intuitive. Graphically, the force begins at the origin and initially increases linearly with . The force then plateaus but eventually increases again and approaches infinity as the chain length approaches . | 7 | Physical Chemistry |
The Journal of the Chemical Society, Faraday Transactions was a peer-reviewed scientific journal published from 1905 until 1998. The journal was originally published by the Faraday Society under the name Transactions of the Faraday Society and was renamed in 1972. | 7 | Physical Chemistry |
Many external factors can influence colour: light, temperature, pH, sugars and metals. There is a method to turn petunia flowers from white to transparent. The petunia flower is immersed into a flask of water, connected to a vacuum pump, after which the flower appeared colourless. The white colour is expressed by the air present in the vacuoles that absorb the light, without air the flower loses the white colour.
There is an increasing interest in flower colour, since some colorations are currently unavailable in plants. Ornamental companies create new flower colour by classical and mutation breeding and biotechnological approaches. For example, white bracts in Poinsettia are obtained by high frequency irradiation. | 1 | Biochemistry |
Electrocatalysis can occur at the surface of some bulk materials, such as platinum metal. Bulk metal surfaces of gold have been employed for the decomposition methanol for hydrogen production. Water electrolysis is conventionally conducted at inert bulk metal electrodes such as platinum or iridium. The activity of an electrocatalyst can be tuned with a chemical modification, commonly obtained by alloying two or more metals. This is due to a change in the electronic structure, especially in the d band which is considered to be responsible for the catalytic properties of noble metals. | 7 | Physical Chemistry |
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